Implement rename folder 2

[Tulsishah]

Description

Implementation of rename folder API in bucket handle and adding corresponding unit tests. This method is not being called from anywhere in the code for now.

Link to the issue in case of a bug fix.

NA

Testing details

1. Manual - NA
2. Unit tests - Added
3. Integration tests - NA

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 72.05%. Comparing base (43e4b64) to head (808315b).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #2101 +/- ## ========================================== + Coverage 71.93% 72.05% +0.11% ========================================== Files 101 101 Lines 10996 11000 +4 ========================================== + Hits 7910 7926 +16 + Misses 2758 2747 -11 + Partials 328 327 -1 ``` | [Flag](https://app.codecov.io/gh/GoogleCloudPlatform/gcsfuse/pull/2101/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleCloudPlatform) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/GoogleCloudPlatform/gcsfuse/pull/2101/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleCloudPlatform) | `72.05% <100.00%> (+0.11%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleCloudPlatform#carryforward-flags-in-the-pull-request-comment) to find out more.

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[ankitaluthra1]

Also update PR description mentioning new method is being called from anywhere or not.